I. Field of the Invention
This invention relates generally to a device for providing electrical stimulation to a patient's body and more particularly to an implantable pulse generator having a headerless design, to thereby significantly reduce the size of the pulse generator. The feed-throughs of the pulse generator are coupled directly to the terminal end of a lead by a connector, thereby connecting several conductors of the lead to the internal circuitry of the pulse generator without the need for a header assembly. The feed-throughs and associated connector are keyed to one another to ensure proper orientation of the mating contacts, and together, provide a means for locking the connector to the feed-throughs without the need for set screws used in conventional prior art systems.
II. Discussion of the Related Art
Various cardiac rhythm management devices capable of pacing or defibrillating a patient's heart comprise a pulse generator having an electronic circuit and power supply contained within a metal housing, commonly referred to as "the can". A lead, capable of transmitting a therapeutic electrical signal generated by the pulse generator to the heart, is coupled to the pulse generator. A receptacle referred to as a "header" is commonly provided for plugging the lead into the device and electrically coupling the lead to the electronic circuit within the can. Representative examples of such devices appear in U.S. Pat. No. 5,545,188, issued to Bradshaw et al. (hereinafter the '188 device) and U.S. Pat. No. 4,934,366, issued to Truex et al. (hereinafter the '366 device). Bradshaw et al. describes a metal housing 10 having a header assembly 14 attached thereto. The header comprises a conductive receptacle embedded in an insulating epoxy and is that portion of the '188 device having connector sockets into which the leads are inserted. The header is attached to the can, wherein conductive wires electrically couple contacts within the socket receptacle of the header to the electronic circuit contained within the can. The conductive wires extend through a hermetic seal insulating member positioned in an opening in the can. The header assembly adds to the overall size and weight of the implanted device.
Treux et al. provides for an implantable medical device having a receptacle assembly formed within the housing of the implantable device. The '366 receptacle assembly includes an elongated barrel divided lengthwise by a plurality of conductive portions separated by insulators. Although the need for a separate molded plastic header assembly has been eliminated, the size and construction of the elongated barrel assembly necessitates an increase in the overall size of the housing of the implantable device.
Over the years, the receptacles located in the header of implantable cardiac rhythm management pulse generators and the terminal connector end of a corresponding lead have been standardized by the International Standards Organization (ISO). In the standard connector and receptacle arrangement, an elongated terminal socket or receptacle is formed in a header portion of the pulse generator and an elongated connector adapted to be received in the socket is formed on the terminal end of the lead.
When a separate header containing the elongated receptacle is attached to the pulse generator, the header and elongated lead connector, together, typically require connector blocks, retaining washers, anchor brackets, anchor pins, and other components necessary to electrically couple the lead to the electronic circuit of the implantable device. Elimination of these components may reduce the overall cost to produce the implantable cardiac rhythm management device and will further reduce its overall size and weight.
During the implantation of a cardiac rhythm management device incorporating ISO accepted pulse generator and leads, the physician must tighten at least one set screw to lock the terminal end of the lead within the receptacle formed in the header. The tightening of set screws requires additional time, extending the overall time in surgery. Also, a threaded bore for receiving the set screw may be stripped if the set screw is over tightened, making it necessary to implant a replacement. Further, during implantation, the physician must create a subcutaneous pocket sufficiently large to accept the pulse generator can or housing, its header, and the terminal end of the lead. These additional surgical steps increase the length of time in surgery and overall cost of implanting the device.
Further, the leads currently used with these standard pulse generators typically have one or more terminal pins associated with each conductor contained within the lead. If more than one conductor and terminal pin are present, the terminal pins include a yoke section between them. When implanting the pulse generator and lead within a patient, the subcutaneous pocket formed by the physician must be made large enough to contain the terminal pins of the lead and the yoke. The elimination of a plurality of pins would further reduce the size of the subcutaneous pocket required to contain the pulse generator and the terminal end of the lead, thereby increasing patient comfort. Also, the elimination of the lead's terminal pins would reduce the total amount of lead ablation when replacing the pulse generator.
Hence, there is a need for a pulse generator and associated lead that may be electrically interconnected without increasing the required overall size of the implanted device. Also there is a need for a pulse generator and associated lead that may be interconnected without requiring a header portion, and wherein the lead has only one terminal connection. The present invention addresses these needs.